Hostility confers increased risk of coronary heart disease, presumably through the mechanism of cardiovascular reactivity to interpersonal stressors. Marriage is an important context for this mechanism. However, an adult developmental perspective suggests that marital conflict may be a more central issue for trait hostility among middle- aged spouses, whereas the stress of collaboration may be important for hostility in older couples. Guided by a model of individual, spouse, and couple effects of hostility, the proposed study examines the effects of hostility on immediate behavioral and psychophysiological responses to marital conflict and collaboration, and on health outcomes of ambulatory blood pressure, coronary artery disease, marital adjustment, and cognitive functioning. The major aims are to examine (a) how the effect of hostility on behavioral and cardiovascular responses may differ for middle-aged and older adults, during conflict and collaborative problem solving, (b) the effect of hostility on ambulatory blood pressure and coronary artery disease, and (c) the role of hostility in the frequency and quality of collaborative problem solving. One-hundred and fifty middle-aged (40-50 years) and 150 older married couples (60-70 years) will be involved in a 4-day study. Hostility will be measured in a multi-method approach with interview, self-report, and spouse report measures. Marital interaction will be examined as couples discuss a source of marital conflict and solve a planning task. Interaction will be coded for components typical of interactions of hostile persons and also detrimental to collaborative cognition. Psychophysiological reactivity will be examined via blood pressure, heart rate, and impedance cardiography during the two tasks. The effects of hostility will be examined on health outcomes such as coronary artery disease (assessed via computed tomography) ambulatory blood pressure, marital adjustment, and general cognitive function (e.g., fluid and crystallized intelligence). The long-term goal of the research is to identify potentially modifiable determinants of cardiovascular risk, marital adjustment, and cognitive aging in adulthood.